1. Field of the Invention
The present invention relates to a fusion splicer and a method for determining an optical fiber type.
2. Description of Related Art
Electric discharge heating conditions for fusion splicing of optical fibers are different depending on the type of the optical fiber. The optimal electric discharge heating conditions for different optical fibers are preliminarily registered in a memory of a fusion splicer. When carrying out fusion splicing work, if the type of the optical fiber prepared for fusion splicing is known, the operator may select a registered electric discharge heating condition based on the type of the optical fiber.
However, there is a case that the type of the target optical fiber is unknown. Optical fibers are very thin, having a diameter of about 125 μm and a core diameter of 10 μm or less. Thus, it is difficult to identify the type of an optical fiber with the naked eye. Usually, the type of the target optical fiber may be automatically determined by the fusion splicer.
In polarization-maintaining optical fibers, a method for measuring lateral imaging graphics by rotating the target optical fiber and determining the type from measuring light transmittance with respect to rotation angle, has been proposed (refer to JP Laid-open No. 2004-341452A (Patent Citation 1)). In polarization-maintaining optical fibers, since nonaxisymmetric stress is given to the core, the fact that luminance characteristics of the transmission images depend on the incident direction of the light, can be utilized. For this reason, the proposed method in Patent Citation 1 may be applied only to polarization-maintaining optical fibers.
In a typical optical fiber, a method for determining the type by comparing a luminance distribution waveform acquired from lateral imaging graphics of the target optical fiber with a reference waveform, is proposed (refer to JP Patent No. 4367597 (Patent Citation 2)). As the reference waveform, a luminance distribution waveform preliminarily measured from a reference optical fiber, is stored in the built-in memory of the fusion splicer.
However, optical fibers are non-circular and thus, have eccentricity. Therefore, the luminance distribution waveform of an optical fiber may vary with measurement direction. For the reference waveform stored in the fusion splicer, usually, the luminance distribution measured from one direction may be used. Also, for the target optical fiber, the luminance distribution may be measured from one direction. Since the luminance distribution of the lateral transmission light may be different depending on the measurement direction, there is a possibility of failure in the determination.
Additionally, when the target optical fiber has not yet been registered in the memory of the fusion splicer, there is a problem that the determination can not be carried out. Alternatively, there is a possibility that the target optical fiber is erroneously determined to be an optical fiber having similar luminance distribution.